What is clock tree specification?

What is a clock tree specification?

CTS spec file contains the below information: 1. Inverters or buffers to be defined which will be used to balance the clock tree. 2. … Contains target Skew, max target transition and other timing constraints as per clock tree.

What are clock tree types?

Up to now, there have been two main methods of clock distribution for large, high-performance designs: conventional clock-tree synthesis (CTS) and clock mesh. Multisource CTS has emerged as a new method that is a hybrid of these two.

What are the contents of the clock spec file?

Clock specification file which contains Insertion delay, skew, clock transition, clock cells, NDR, CTS tree type, CTS exceptions, list of buffers/inverters etc…

What is spec in VLSI?

The “specs” typically describe the expected functionality (Boolean operations) of the designed block, as well as the maximum allowable delay times, the silicon area and other properties such as power dissipation.

What is clock tree design?

A clock tree is a clock distribution network within a system or hardware design. It includes the clocking circuitry and devices from clock source to destination. The complexity of the clock tree and the number of clocking components used. depends on the hardware design.

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Why is CTS needed?

The goal of CTS is to minimize the skew and latency. … Clock tree can be build by clock tree inverters so as to maintain the exact transition (duty cycle) and clock tree balancing is done by clock tree buffers (CTB) to meet the skew and latency requirements.

What is clock tree optimization?

It primarily focuses on timing, power and area optimization by applying different optimization techniques at each stage of the design. Clock Tree Synthesis (CTS) is an important step in physical design flow. CTS builds the clock tree by balancing the skew in the entire design for all the clocks present.

Which is better buffer or inverter?

In most of the library files, a buffer is the combination of two inverters so we can say that inverter will be having lesser delay than buffer with the same drive strength. Also inverters having more driving capacity than a buffer that’s why most of the libraries preferred inverter over buffer for CTS.

What is skew and latency?

Clock Skew between two sink pins is the the difference in the clock latency between them. If the capture clock latency is more than the launch clock, then it is positive skew. … If the capture clock latency is less than the launch clock, then it is negative skew. This helps hold checks.

What is clock tree synthesis in physical design?


CTS is the process of connecting the clocks to all clock pin of sequential circuits by using inverters/buffers in order to balance the skew and to minimize the insertion delay. All the clock pins are driven by a single clock source.

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What is latency in VLSI?

When describing a digital circuit there are two other important factors: latency and throughput. Latency is the time needed for an input change to produce an output change; latency can be expressed as a length of time or, in synchronous circuits, as a certain number of clock cycles.

What are clock tree exceptions?

Clock Tree Exceptions

Non- Stop Pin. Exclude Pin. Float Pin. Stop Pin. Don’t Touch Subtree.

What is VLSI design flow?

VLSI Design Flow

The various levels of design are numbered and the blocks show processes in the design flow. Specifications comes first, they describe abstractly, the functionality, interface, and the architecture of the digital IC circuit to be designed.

What are the different checks we do in CTS stage?

CTS Quality Checks

There are following quality checks for the Clock Tree Synthesis: Minimize Insertion Delay. Skew Balancing. Duty Cycle.

What will you do if insertion delay and skew are not met?

If you do not meet timing either you can skew or deskew for some flops, so in that case your skew is more than your target skew for those flops.